The present invention relates to a pad holding spring of a brake pad for a disc brake having a spring piece, which can be mounted in a manner that is secure against loss and allows radial deflection on an edge of the pad carrier plate, as well as to a brake pad holding arrangement for a disc brake of a motor vehicle.
Pad holding springs of this kind are normally used in prior-art brake pad holding arrangements of brake pad systems. In these brake pad systems, brake pads are respectively arranged on both sides of a brake disc, each brake pad having a friction pad and a pad carrier plate carrying the friction pad. The brake pads are held under a radial spring load in a manner secured by a pad holding spring of each brake pad in a pad slot of a fixed brake carrier having brake carrier horns on the leading-edge side and the trailing-edge side laterally enclosing the brake pads.
A pad holding spring of the type in question is known from DE 40 20 287 A1, for example. In this case, the pad holding spring, which is designed as a leaf spring, is secured on the brake pad carrier on holding lugs projecting from an outer edge of the brake pad carrier, by which the pad holding spring is held both in and counter to the direction of rotation of the brake disc and also radially with respect to the axis of rotation of the brake disc.
The inner sides of the brake carrier horns laterally delimiting the pad slot are usually aligned parallel to one another, allowing a brake pad formed with two lateral edges aligned parallel to one another to be introduced radially into the pad slot from above and secured with the aid of the pad holding spring. The brake pads are spanned by a pad holding bracket which thus contributes to stabilization of the brake pads by counteracting accelerations or shaking loads caused by external forces acting from outside transversely to the direction of application.
These transverse forces acting on the pad during the braking process must be introduced into the brake carrier via the brake carrier horns. However, it is generally not possible to embody the supporting surfaces of these brake carrier horns in an optimum manner, owing to limited installation space conditions, the result being that the movements of the brake pad during a braking process also include a rotary motion. Such rotary motions can have a negative effect on the release clearance, namely the free travel between the brake pad and the brake disc, and on the wear behaviour of the brake pads, e.g. in the form of oblique wear.
It is always necessary to guide and fix the brake pads reliably in the brake carrier in order to ensure reliable functioning of the disc brake.
In the case of newer brake pad concepts with asymmetrically formed brake pads, the brake pad is guided at one lateral end face by means of positive engagement with an inner side of a carrier horn of the brake carrier. During assembly, the brake pad can thus be inserted into the pad slot between the carrier horns by way of a pivoting movement, ensuring that, after pivoting of the brake pad into the working position between the carrier horns, the opposite lateral end face of the brake pad lies in front of the inner side of the opposite carrier horn, said side facing the brake pad, and has radial freedom of movement.
If this brake pad then lifts off radially upwards owing to external forces acting on the free side from the outside, transversely to the direction of application, the distance between the brake pad and said carrier horn increases and the brake pad is neither retarded nor hindered in any other way in its movement radially away from the brake disc.
In this case, even the preloading force of the pad holding spring supported on the pad holding bracket cannot absorb these externally acting forces, and therefore the brake pad has such a large freedom of movement that, when it falls back into its initial position after such a pivoting movement, it strikes the supporting surface at the bottom of the pad slot, and this can lead to fracture or cracking of the friction pad of the brake pad.
It is the object of the present invention to provide a pad holding spring and a brake pad holding arrangement for a disc brake which ensure fixing of the brake pads in the brake carrier in such a way that a radial pivoting movement of the brake pad out of the pad slot can be largely prevented.
This object is achieved by a pad holding spring of a brake pad having a spring section, which can be mounted in a manner that is secure against loss and allows radial deflection on an edge of the pad carrier plate. The pad holding spring has a subsection which is designed as a wedging section and which extends at an angle from one end of the spring section of the pad holding spring and by a brake pad holding arrangement for a brake pad having such a pad holding spring for a disc brake of a motor vehicle.
In addition to a pad holding spring part designed as a spring section, which can be mounted in a manner that is secure against loss and allows radial deflection on an edge of the pad carrier plate, the pad holding spring according to the invention has a subsection which is designed as a wedging section and which extends at an angle from one end of the spring section of the pad holding spring.
In the brake pad holding arrangement according to the invention, the pad holding spring is designed in a corresponding manner in such a way that, in the mounted position, a subsection of the pad holding spring extends over that edge of the pad carrier plate which faces the brake carrier horn on the trailing-edge side and into a gap between the brake carrier horn on the trailing-edge side and that lateral edge of the pad carrier plate which faces the brake carrier horn on the trailing-edge side.
On the one hand, this allows simple mounting of the pad holding spring on the brake pad and of the brake pad with the pad holding spring mounted thereon in the pad slot of the brake carrier between the brake carrier horns. On the other hand, after the mounting of the pad holding spring and the insertion of the brake pad into the pad slot, this prevents the brake pad from being twisted out during a braking process by virtue of the wedging action of the subsection of the pad holding spring on that lateral edge of the pad carrier plate of the brake pad which faces the brake carrier horn on the trailing-edge side.
According to an advantageous variant embodiment of the invention, the subsection of the pad holding spring is of rectilinear design, allowing very simple mounting of the pad holding spring in the gap between the pad carrier plate and the brake carrier horn.
It is also contemplated, depending on the width of the gap between the pad carrier plate and the pad carrier horn on the trailing-edge side, for the subsection of the pad holding spring to be embodied as at least partially undulating or serrated transversely to the longitudinal extent of the subsection and to the direction of rotation of the brake pad, thereby also making it possible in a simple manner reliably to prevent the brake pad from being twisted out of a gap with a relatively large gap width.
According to an advantageous development of the invention, a transitional subsection is provided between the spring section and the subsection of the pad holding spring. This transitional subsection is of arc-shaped design and, in particular, runs in an arc around a corner region of the pad carrier plate. This makes the mounting of the pad holding spring in its functional position even easier. In addition, this ensures that, by virtue of wedging of the subsection of the pad holding spring between the brake carrier horn on the trailing-edge side and the side wall of the pad carrier plate, slight twisting out of the brake pad does not lead to release of the joint between the pad holding spring and that edge of the pad carrier plate which faces away from the axis of rotation of the brake disc since, in this case, the transitional subsection can be deformed out of the arc-shaped configuration with a predetermined radius into a shape with an enlarged radius and thus provides the necessary length compensation.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.